ion of the shape of the earth, we came to the conclusion that
the aetherial atom was a spherical vortex atom, or, to be more correct,
that it was an oblate spheroid with its polar diameter, so to speak,
shorter than its equatorial diameter, and further, that the aetherial
atom possessed polarity.

Now if we can conceive of these aetherial vortex atoms being joined
together, North pole to South pole, and revolving round their axes, we
shall then have an exact image of Maxwell's physical conception of
Faraday's Lines of Force.

We know that when any liquid body is caused to rotate rapidly about its
axis, it will expand laterally and contract longitudinally in the
direction of the axis; and it was on this analogy that Maxwell worked
out his physical conception of the lines of force. Maxwell's fundamental
idea was, that in a magnetic field there is a rotation of the molecule
ever going on about the lines of force. For example, let _A_ _B_ be a
magnet, and _A_ _C_ _B_ be a line of force composed of spherical vortex
atoms joined end to end, that is, each North pole (assuming the vortex
atoms to be magnets) being directly associated with the South pole of
the one next to it, and _vice-versa_ (Fig. 20).

Thus it can be readily seen that there will be a tension along the line
of force, while there will be a pressure at right angles to it owing to
the lateral expansion, partly due to the rotation of the vortex atom,
and partly due to the attraction of the vortices for each other in the
direction of the line of force.

Maxwell in his paper says: "It appears therefore that the stress in the
axis of the line of magnetic force is a tension like that of a rope."
Further, he adds: "Let us now suppose that the phenomena of magnetism
depend upon the existence of the tension in the direction of the lines
of force, combined with a hydrostatic pressure, or in other words, a
pressure greater in the equatorial than in the axial direction. The next
question is, What mechanical explanation can we give of these
inequalities of pressure in a fluid or mobile medium? The explanation
which most readily occurs to the mind is, that the excess of pressure in
the equatorial direction arises from the centrifugal force of the
vortices or eddies in the medium, having their axes in the direction
parallel to the lines of force." He adds: "A medium of this kind filled
with molecular vortices, having their axes parallel, differs from an
ordinary medium in